Variations in the polar cap area during two substorm cycles
Steve Milan,Mark Lester,Stanley W. H. Cowley,Kjellmar Oksavik,Mitchell J. Brittnacher,R. A. Greenwald,George J. Sofko,Jean-Paul Villain +7 more
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In this article, the authors employed observations from several sources to determine the location of the polar cap bound-ary, or open/closed field line boundary, at all local times, allowing the amount of open flux in the magnetosphere to be quantified.Abstract:
This study employs observations from several sources to determine the location of the polar cap bound- ary, or open/closed field line boundary, at all local times, allowing the amount of open flux in the magnetosphere to be quantified. These data sources include global auroral im- ages from the Ultraviolet Imager (UVI) instrument on board the Polar spacecraft, SuperDARN HF radar measurements of the convection flow, and low altitude particle measurements from Defense Meteorological Satellite Program (DMSP) and National Oceanographic and Atmospheric Administration (NOAA) satellites, and the Fast Auroral SnapshoT (FAST) spacecraft. Changes in the open flux content of the mag- netosphere are related to the rate of magnetic reconnection occurring at the magnetopause and in the magnetotail, al- lowing us to estimate the day- and nightside reconnection voltages during two substorm cycles. Specifically, increases in the polar cap area are found to be consistent with open flux being created when the IMF is oriented southwards and low-latitude magnetopause reconnection is ongoing, and de- creases in area correspond to open flux being destroyed at substorm breakup. The polar cap area can continue to de- crease for 100 min following the onset of substorm breakup, continuing even after substorm-associated auroral features have died away. An estimate of the dayside reconnection voltage, determined from plasma drift measurements in the ionosphere, indicates that reconnection can take place at all local times along the dayside portion of the polar cap bound- ary, and hence presumably across the majority of the dayside magnetopause. The observation of ionospheric signatures of bursty reconnection over a wide extent of local times sup- ports this finding.read more
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A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions
Gareth Chisham,Mark Lester,Steve Milan,Mervyn P. Freeman,William A. Bristow,Adrian Grocott,Kathryn A. McWilliams,J. M. Ruohoniemi,Tim K. Yeoman,Peter. Dyson,R. A. Greenwald,Takashi Kikuchi,Michael Pinnock,J.P.S. Rash,Noriaki K. Sato,George J. Sofko,Jean-Paul Villain,Anthony Walker +17 more
TL;DR: The Super Dual Auroral Radar Network (SuperDARN) as discussed by the authors has been operating as an international co-operative organization for over 10 years and has been successful in addressing a wide range of scientific questions concerning processes in the magnetosphere, ionosphere, thermosphere, and mesosphere, as well as general plasma physics questions.
Journal ArticleDOI
Substorm Current Wedge Revisited
Larry Kepko,Robert L. McPherron,Olaf Amm,S. Apatenkov,Wolfgang Baumjohann,J. Birn,Mark Lester,Rumi Nakamura,Tuija Pulkkinen,V. A. Sergeev +9 more
TL;DR: In this article, the substorm current wedge was developed to explain the magnetic signatures observed on the ground and in geosynchronous orbit during substorm expansion, and new observations, including radar and low altitude spacecraft, MHD simulations, and theoretical considerations have tremendously ad-vanced our understanding of this system.
Journal ArticleDOI
Magnetic flux transport in the Dungey cycle: A survey of dayside and nightside reconnection rates
TL;DR: In this paper, changes in the open flux content of the ionospheric polar cap, estimated from auroral, radar, and low-Earth orbit particle measurements, are used to determine dayside and nightside reconnection rates during 73 hours of observation spread over nine intervals.
Journal ArticleDOI
Morphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter
John Clarke,Jean-Claude Gérard,Denis Grodent,S. Wannawichian,Jacques Gustin,John E. P. Connerney,F. J. Crary,M. K. Dougherty,William S. Kurth,Stanley W. H. Cowley,Emma J. Bunce,T. W. Hill,Jungeol Kim +12 more
TL;DR: In this article, the authors report ultraviolet images of Saturn, which, when combined with simultaneous Cassini measurements of the solar wind and Saturn kilometric radio emission, demonstrate that its aurorae differ morphologically from those of both Earth and Jupiter.
Journal ArticleDOI
Review of the accomplishments of mid-latitude Super Dual Auroral Radar Network (SuperDARN) HF radars
Nozomu Nishitani,J. M. Ruohoniemi,Mark Lester,J. B. H. Baker,A. V. Koustov,Simon G. Shepherd,Gareth Chisham,Tomoaki Hori,Evan G. Thomas,Roman A. Makarevich,Aurélie Marchaudon,P. V. Ponomarenko,Jim Wild,Stephen E. Milan,William A. Bristow,John Devlin,Ethan S. Miller,R. A. Greenwald,Tadahiko Ogawa,Takashi Kikuchi +19 more
TL;DR: The Super Dual Auroral Radar Network (SuperDARN) is a network of highfrequency (HF) radars located in the high and mid-latitude regions of both hemispheres that is operated under international cooperation as mentioned in this paper.
References
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Journal ArticleDOI
Electron polar cap and the boundary of open geomagnetic field lines
L. C. Evans,E. C. Stone +1 more
TL;DR: The boundary of the electron polar cap, which should occur at the latitude separating open and closed field lines, is consistent with previously reported closed field line limits determined from trapped-particle data as mentioned in this paper.
The Electron Polar Cap and the Boundary of the Open Geomagnetic Field Lines
L.L.C. Evans,E. C. Stone +1 more
TL;DR: The boundary of the electron polar cap, which should occur at the latitude separating open and closed field lines, is consistent with previously reported closed field line limits determined from trapped-particle data.
Journal ArticleDOI
Properties of localized, high latitude, dayside aurora
Harald U. Frey,Thomas J. Immel,Gang Lu,John W. Bonnell,S. A. Fuselier,Stephen B. Mende,Benoît Hubert,Nikolai Østgaard,Guan Le +8 more
TL;DR: In this paper, the authors describe a completely different type of high latitude aurora, which does not show any signature of precipitating protons and also occurs during northward interplanetary magnetic field (IMF) and high solar wind dynamic pressure periods.
Journal ArticleDOI
A case study of HF radar spectra and 630.0 nm auroral emission in the pre midnight sector
TL;DR: In this article, a comparison of HF radar backscatter observed by the CUTLASS Finland radar, meridian scanning photometer data from Longyearbyen, magnetic field variations from IMAGE stations, and particle precipitation measured by the DMSP F12 spacecraft is presented.
Journal ArticleDOI
SCIFER‐Dayside auroral signatures of magnetospheric energetic electrons
D. A. Lorentzen,Charles Deehr,Joseph I. Minow,Roger W. Smith,H. C. Stenbaek-Neielsen,Fred Sigernes,Roger L. Arnoldy,K. A. Lynch +7 more
TL;DR: The SCIFER sounding rocket was launched over the dayside aurora, at 10 hr Magnetic Local Time (MLT) on January 25, 1995 as mentioned in this paper on Svalbard under the flight apogee.